Preparation

In a large enameled cast-iron casserole, heat olive oil until shimmering. Add chuck and sirloin and cook over moderately high heat, breaking up meat into large chunks, until no pink remains. Add garlic, oregano and crushed red pepper and cook until fragrant. Stir in tomato paste and cook until meat is coated. Add tomatoes and their juices and tomato puree along with chicken stock, bay leaves, thyme and sugar. Season with salt and pepper and bring to a boil. Simmer over moderate heat, stirring occasionally, until thickened and reduced to 8 cups, about 1 1/2 hours. Remove bay leaves and thyme sprigs. Meanwhile, heat a large skillet. Add sausage meat in large pieces and cook over moderately high heat until browned and just cooked through, about 10 minutes. Drain sausage and break it into 1/2-inch pieces. In a large bowl, combine ricotta with parsley, basil and 1/4 cup of the Parmesan. Add two-thirds of shredded mozzarella and season with salt and pepper. Beat in egg. Cook lasagna noodles in a large pot of boiling salted water, stirring occasionally, until al dente. Drain noodles and rinse under cold water. Dry noodles between layers of paper towels. Preheat oven to 375°. Spread 1 cup of sauce in bottom of a 9-by-13-inch glass baking dish. Line dish with 4 overlapping noodles. Spread one-half of the ricotta mixture over noodles, then top with one-half of the sausage, 1 1/2 cups of sauce and another 4 noodles. Repeat layering with remaining ricotta, sausage and another 1 1/2 cups of sauce. Top with 4 noodles and cover with 1 1/2 cups of sauce. Toss remaining 1 cup of mozzarella with remaining 1/4 cup of Parmesan and sprinkle over lasagna. Bake lasagna for about 45 minutes, or until the top is golden & crisp around edges and filling is bubbling. Let lasagna rest for 20 minutes before serving.

Make Ahead The lasagna can be prepared through Step 5 and refrigerated overnight, or it can be baked ahead and then reheated in 325° oven.